x_tables: ip6_tables: REJECT target: used from hooks POSTROUTING, but only usable from INPUT/FORWARD/OUTPUT ====================================================== WARNING: possible circular locking dependency detected 4.14.181-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.1/32290 is trying to acquire lock: (&ovl_i_mutex_key[depth]){+.+.}, at: [] inode_lock include/linux/fs.h:719 [inline] (&ovl_i_mutex_key[depth]){+.+.}, at: [] bprm_fill_uid fs/exec.c:1524 [inline] (&ovl_i_mutex_key[depth]){+.+.}, at: [] prepare_binprm+0x31a/0x7e0 fs/exec.c:1559 but task is already holding lock: (&sig->cred_guard_mutex){+.+.}, at: [] prepare_bprm_creds+0x51/0x110 fs/exec.c:1391 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: x_tables: ip6_tables: REJECT target: used from hooks POSTROUTING, but only usable from INPUT/FORWARD/OUTPUT -> #3 (&sig->cred_guard_mutex){+.+.}: __mutex_lock_common kernel/locking/mutex.c:756 [inline] __mutex_lock+0xe8/0x1430 kernel/locking/mutex.c:893 lock_trace+0x3f/0xc0 fs/proc/base.c:407 proc_pid_stack+0x10b/0x240 fs/proc/base.c:457 proc_single_show+0xe7/0x150 fs/proc/base.c:761 seq_read+0x4d2/0x1130 fs/seq_file.c:237 do_loop_readv_writev fs/read_write.c:695 [inline] do_loop_readv_writev fs/read_write.c:682 [inline] do_iter_read+0x3e3/0x5a0 fs/read_write.c:919 vfs_readv+0xd3/0x130 fs/read_write.c:981 do_preadv+0x161/0x200 fs/read_write.c:1065 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb -> #2 (&p->lock){+.+.}: __mutex_lock_common kernel/locking/mutex.c:756 [inline] __mutex_lock+0xe8/0x1430 kernel/locking/mutex.c:893 seq_read+0xba/0x1130 fs/seq_file.c:165 proc_reg_read+0xf2/0x160 fs/proc/inode.c:217 do_loop_readv_writev fs/read_write.c:695 [inline] do_loop_readv_writev fs/read_write.c:682 [inline] do_iter_read+0x3e3/0x5a0 fs/read_write.c:919 vfs_readv+0xd3/0x130 fs/read_write.c:981 kernel_readv fs/splice.c:361 [inline] default_file_splice_read+0x41d/0x870 fs/splice.c:416 do_splice_to+0xfb/0x150 fs/splice.c:880 splice_direct_to_actor+0x20a/0x730 fs/splice.c:952 do_splice_direct+0x164/0x210 fs/splice.c:1061 do_sendfile+0x469/0xaf0 fs/read_write.c:1441 SYSC_sendfile64 fs/read_write.c:1502 [inline] SyS_sendfile64+0xff/0x110 fs/read_write.c:1488 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb -> #1 (sb_writers#3){.+.+}: percpu_down_read_preempt_disable include/linux/percpu-rwsem.h:36 [inline] percpu_down_read include/linux/percpu-rwsem.h:59 [inline] __sb_start_write+0x1a1/0x2e0 fs/super.c:1363 sb_start_write include/linux/fs.h:1549 [inline] mnt_want_write+0x3a/0xb0 fs/namespace.c:386 ovl_link+0x60/0x18d fs/overlayfs/dir.c:594 vfs_link+0x637/0xa60 fs/namei.c:4264 SYSC_linkat fs/namei.c:4332 [inline] SyS_linkat+0x370/0x570 fs/namei.c:4288 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb -> #0 (&ovl_i_mutex_key[depth]){+.+.}: lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998 down_write+0x34/0x90 kernel/locking/rwsem.c:54 inode_lock include/linux/fs.h:719 [inline] bprm_fill_uid fs/exec.c:1524 [inline] prepare_binprm+0x31a/0x7e0 fs/exec.c:1559 do_execveat_common.isra.0+0xcb5/0x1c50 fs/exec.c:1785 do_execve fs/exec.c:1847 [inline] SYSC_execve fs/exec.c:1928 [inline] SyS_execve+0x34/0x40 fs/exec.c:1923 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb other info that might help us debug this: Chain exists of: &ovl_i_mutex_key[depth] --> &p->lock --> &sig->cred_guard_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&sig->cred_guard_mutex); lock(&p->lock); lock(&sig->cred_guard_mutex); lock(&ovl_i_mutex_key[depth]); *** DEADLOCK *** 1 lock held by syz-executor.1/32290: #0: (&sig->cred_guard_mutex){+.+.}, at: [] prepare_bprm_creds+0x51/0x110 fs/exec.c:1391 stack backtrace: CPU: 1 PID: 32290 Comm: syz-executor.1 Not tainted 4.14.181-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x1b2/0x283 lib/dump_stack.c:58 print_circular_bug.isra.0.cold+0x2dc/0x425 kernel/locking/lockdep.c:1258 check_prev_add kernel/locking/lockdep.c:1905 [inline] check_prevs_add kernel/locking/lockdep.c:2022 [inline] validate_chain kernel/locking/lockdep.c:2464 [inline] __lock_acquire+0x3057/0x42a0 kernel/locking/lockdep.c:3491 lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998 down_write+0x34/0x90 kernel/locking/rwsem.c:54 inode_lock include/linux/fs.h:719 [inline] bprm_fill_uid fs/exec.c:1524 [inline] prepare_binprm+0x31a/0x7e0 fs/exec.c:1559 do_execveat_common.isra.0+0xcb5/0x1c50 fs/exec.c:1785 do_execve fs/exec.c:1847 [inline] SYSC_execve fs/exec.c:1928 [inline] SyS_execve+0x34/0x40 fs/exec.c:1923 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x45ca29 RSP: 002b:00007f32c3774c78 EFLAGS: 00000246 ORIG_RAX: 000000000000003b RAX: ffffffffffffffda RBX: 00000000004db840 RCX: 000000000045ca29 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000000 RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 00000000000000a8 R14: 00000000004c35ac R15: 00007f32c37756d4 overlayfs: './file0' not a directory x_tables: ip6_tables: REJECT target: used from hooks POSTROUTING, but only usable from INPUT/FORWARD/OUTPUT x_tables: ip6_tables: REJECT target: used from hooks POSTROUTING, but only usable from INPUT/FORWARD/OUTPUT x_tables: ip6_tables: REJECT target: used from hooks POSTROUTING, but only usable from INPUT/FORWARD/OUTPUT x_tables: ip6_tables: REJECT target: used from hooks POSTROUTING, but only usable from INPUT/FORWARD/OUTPUT x_tables: ip6_tables: REJECT target: used from hooks POSTROUTING, but only usable from INPUT/FORWARD/OUTPUT x_tables: ip6_tables: REJECT target: used from hooks POSTROUTING, but only usable from INPUT/FORWARD/OUTPUT x_tables: ip6_tables: REJECT target: used from hooks POSTROUTING, but only usable from INPUT/FORWARD/OUTPUT x_tables: ip6_tables: REJECT target: used from hooks POSTROUTING, but only usable from INPUT/FORWARD/OUTPUT